1. Field of the Invention
The invention relates to the field of multi-purpose residential plumbing and fire sprinkler systems. A multi-purpose residential plumbing and fire sprinkler system or, more simply, a multipurpose piping system ("MPS") is a system for providing water to both domestic uses (e.g., showers, sinks, toilets) and to sprinklers for fire protection. The invention provides an apparatus and method for alarming when one or more sprinklers connected to the MPS are activated by a fire. In particular, the invention provides an apparatus and method for distinguishing typical domestic water flow from the flow caused by one or more sprinkler heads.
2. Description of the Prior Art
The National Fire Protection Association ("NFPA") has established standards for the design and operation of multi-purpose residential fire sprinkler systems. The standard is known as NFPA 13D, 1996 Ed. It defines a multipurpose piping system as "[a] piping system within dwellings and manufactured homes intended to serve both domestic and fire protection needs."
Typical commercial fire sprinkler systems utilize a water flow detector to provide an alarm means. When a flow of sufficient volume is detected, typical commercial systems indicate an alarm condition. The only reason that water typically flows in commercial systems is activation of a sprinkler head. Therefore, in a typical commercial system an alarm means need only determine whether or not water is flowing.
In an MPS water regularly flows through the common piping. Flows occur to supply domestic needs within the residence. Whenever a sink, shower or toilet valve open, water flows in the MPS. Therefore, the alarm system used on typical commercial applications will not work for MPS because simply taking a shower would cause a typical commercial flow detector to alarm when used with an MPS.
In light of this problem, typical residential applications have two completely different piping systems: (1) a fire sprinkler piping system, and (2) a domestic piping system. This basically doubles the number of pipes and the amount of plumbing work which has to be performed in a typical residential application. The same set of piping cannot be used for both systems because the flow alarm would send false signals every time domestic water was turned on. Alternatively, a residential application could use a fire detection system (i.e., electronic fire sensor system). However, a fire detection system does not alarm when water flows. Therefore, with a fire detection system and no flow alarm, the fire sprinklers could run for days, causing extensive water damage, while the home owner is away on vacation and no alarm would sound.